1. Field of the Invention
The present invention relates to a bisphosphonic acid derivative having an affinity to the bone, the bisphosphonic acid derivative labeled with a radioactive nuclide, a method for labeling the bisphosphonic acid derivative with the radioactive nuclide, and a radioactive agent for diagnosis or therapy of bone disease, containing the bisphosphonic acid derivative labeled with the radioactive nuclide as the active ingredient.
2. Related Art
In recent years, a scintigraphy of the skeleton in methods of nuclear medicine becomes one of the important test methods in its early stage for diagnosis of the bone disease. As to an imaging agent used for scintigraphy of the bone, said agent requires shorten intervals between the administration of the imaging agent and the timing of taking a scintigram, further such agent should have the properties of high affinity to the bone and of efficient urinary excretion, as well as rapid clearances from the blood and non-osseous tissues.
At present, a phosphonic acid derivative labeled with a radioactive isotope may be used for the above-mentioned purposes, and an inorganic polyphosphonic acid labeled with 99m-Technetium was used as the first example therefor. However, such inorganic polyphosphonic acids labeled with 99m-Technetium perform inevitably the lower clearance from the blood, because such compounds may be changed to the corresponding monophosphates by hydrolysis in aqueous solutions.
In order to solve such problems, Yano, et al. reported stannous Tc-99m-ethane-1-hydroxy-1,1-diphosphonate (Tc-99m-HEDP), which is an organic diphosphonic acid labeled with 99m-Technetium [J. Nucl. Med., 14, 73, (1973) and U.S. Pat. No. 3,735,001)]. By use of said compound, the bone scintigraphy can be carried out in the earlier stage of test after the compound is administered, because this compound has property of relatively rapid clearance from the blood. For this reason, compounds of phosphonic acid labeled with 99m-Technetium, which are compounds similar to Tc-99m-HEDP, for example compounds relating to organic diphosphonic acid, such as methanediphosphonic acid (MDP), 3,3-diphosphono-1,2-propanedicarboxylic acid (DPD) and hydroxymethanediphosphonic acid (HMDP) and the like, being labeled with 99m-Technetium are widely used for this purpose. These compounds are used for pharmaceutical preparations for bone scintigraphy, which can deposit or accumulate to the sites where calcification of the bone is taken place, and such compounds make an interval between the administration of the imaging agent and the timing of taking a scintigram shorten. However, these compounds are still not good enough in connection with the waiting time, because they require waiting time for about 3 hours after the administration of compound to take a scintigram.
Generally, in conducting a bone scintigraphy, when the radioactivity of imaging agent disappears slowly from the blood and/or soft tissue with the slower urinary excretion, then a certain length of time for lowering the background of radioactivity is required, and it is necessary to have the longer waiting time for taking a scintigram after the administration of imaging agent. When a phosphonic acid compound labeled with Technetium is used, the polymer structure thereof may be considered as one of the factors for giving influence on the clearance. The phosphonic acid compound labeled with Technetium may give high possibility of affecting the clearance due to the formation of polymer structure. Attempt at realizing the rapid clearance in the earlier stage after the administration of an imaging agent by changing the polymer structure of the radiolabeled bisphosphonic acid compound to monomolecular structure has been made with a bisphosphonate compound labeled with 123-Iodine (WO 89/11877), but satisfactory result has not been obtained yet. When a possible coordination site for a radioactive metal, other than the phosphonic acid group, is introduced to a bisphosphonate compound, the compound labeled with a radioactive metal might give a stable monomolecular structure. However, such trial described above with available compounds for use in bone scintigraphy has not been carried out and, of course, properties of the resultant monomolecular compound as a bone imaging agent have not been examined.
Under the circumstances, an object of the present invention is to provide a bisphosphonic acid derivative having the properties of rapid accumulation to the bone and rapid urinary excretion, and a compound thereof labeled with a radioactive nuclide.
The present invention provides a bisphosphonic acid derivative or salt thereof represented by the following formula (1):
Rxe2x80x94Yxe2x80x94Axe2x80x83xe2x80x83(1)
wherein A is a bisphosphonic acid or salt thereof, having a Pxe2x80x94Cxe2x80x94P bond; Y is a bonding portion selected from the group consisting of xe2x80x94(CH2),xe2x80x94, xe2x80x94[(CH2)m(NHCO)r(CH2)n]qxe2x80x94, xe2x80x94[(CH2)m(CONH)r(CH2)n]qxe2x80x94 and xe2x80x94(CH2)oxe2x80x94Sxe2x80x94(CH2)pxe2x80x94; k, l, m, n, o, p, q, and r are each represents independently an integer, and k=0 or 1; l=0 to 6; m=0 to 6; n=1 to 6; o=0 to 6, p=0 to 6; q=1 to 6; and r=1 to 6; R is a group of any one of compounds selected from the group consisting of a polyaminopolycarboxylic acid, an aliphatic carboxylic acid, a mercaptoacetylpolyamino acid or its derivative and a compound represented by the following formula (2), 
and in the formula (2), X is a halogen atom or its isotope, or alkyl tin; Z is a group of any one of compounds selected from the group consisting of an aminocarboxylic acid, an alkylcarboxylic acid, a substituted-alkylcarboxylic acid, an alkylsulfonic acid and a substituted-alkyl sulfonic acid.
A radiolabeled bisphosphonic acid derivative prepared by labeling the above-mentioned bisphosphonic acid derivative with a radioactive nuclide is useful as an active ingredient of radiopharmaceutical for the bone scintigraphy or the bone disease therapy, and as to preferable radioactive nuclides, 99m-Technetium, 111-Indium, 117m-Tin, 153-Samarium, 186-Rhenium, 188-Rhenium, 123-Iodine, 125-Iodine, 131-Iodine, 211-Astatine and the like can be exemplified.
The above-mentioned bisphosphonic acid derivative labeled with radioactive nuclide represented by the formula (1), wherein R is a group being labeled with radioactive halogen or a radioactive transition metal; and A is a free form of bisphosphonic acid or salt thereof without participating in the formation of complex with said radioactive transition metal or other metal, is one of the embodiments of the present invention and is useful as the active ingredient of a radiopharmaceutical for the bone scintigraphy or the bone disease therapy.
Another embodiment of the present invention is, in case of labeling the bisphosphonic acid derivative with a radioactive transition metal, a labeling method that a bisphosphonic acid derivative is allowed to react with a peracid ion of radioactive transition metal in the presence of non-metallic reducing agent to form a complex.
Preferably, said peracid ion of the radio-active transition metal is selected from any one of the group consisting of pertechnetate (Tc-99m), perrhenate (Re-186), and perrhenate (Re-188); and the non-metallic reducing agent is selected from any one of the group consisting of sodium diphenylphosphinobenzene-3-sulfonate, formamidinesulfonic acid and glucoheptanoic acid.
The present invention provides, as represented by the above-mentioned formula (1), a bisphosphonic acid derivative wherein a bisphosphonic acid having the affinity to the bone is combined with a group capable of being labeled with a radioactive transition metal or a radioactive halogen. The bisphosphonic acid derivative having the affinity to the bone can be used as the active ingredient of agent for diagnosis or therapy of bone disease by radiolabeling.
In the formula (1), A is alpha-geminal-bisphosphonic acid, i.e., bisphosphonic acid having Pxe2x80x94Cxe2x80x94P bond, or its derivative. To the alpha-carbon atom, bonding group exemplified by Y is attached and an atom or a group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, a carboxylic acid group, a sulfonic acid group, a lower alkyl group, a lower alkylalcohol group and a cyano group may be also attached to the alpha-carbon. Methanediphosphonic acid (MDP), hydroxymethane-diphosphonic acid (HMDP), 1-hydroxyethane-1,1-bisphosphonic acid (EHDP), dimethylaminomethylene-diphosphonic acid (DMAD), 3,3-diphosphono-1,2-propanedicarboxylic acid (DPD) and salts thereof are exemplified as alpha-geminal-bisphosphonic acid without being substituted with group Y.
In the formula (2) as one of the groups of R, the aminocarboxylic acid indicated as symbol Z can be exemplified as glycine, alanine, asparagic acid, glutamic acid, etc.; the alkyl group as indicated in the alkylcarboxylic acid, substituted alkylcarboxylic acid, alkylsulfonic acid, and substituted alkylsulfonic acid can be exemplified as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, hexyl group, cyclohexyl group, pentadecanyl group, hexadecanyl group, etc. As to the substituted alkyl group, hydroxyalkyl group, halogenated alkyl group, cyanoalkyl group, etc. can be exemplified.
The symbol X in the formula (2) is a hologen atom or isotopes thereof, and exemplified as iodine, chlorine, bromine, fluorine, astatine, etc., and radioactive isotopes thereof. Among them, 123-Iodine, 125-Iodine, 131-Iodine may be used preferably. Further, X, as a precursor, may be substituted by a halogen atom or trialkyl tin, and a substitute group which can be easily substituted by a halogen atom or its isotope may be used, and bromine, trimethyl tin, tributyl tin etc. may be exmplified. The bonding positions of X and Z as the substituents in the phenyl group are not specifically restricted, preferably X is bonded at ortho-position or meta-position to the position of Z.
As to the polyaminopolycarboxylic acid, for example, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylene-tetraminehexaacetic acid (TTHA), and hydroxyethylene-diaminetriacetic acid (HEDTA) may be used.
As to the aliphatic carboxylic acid, alkylcarboxylic acid, substituted alkylcarboxylic acid, etc. may be exemplified, and as to the alkyl group, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, hexyl group, cyclohexyl group, pentadecanyl group, hexadecanyl group, etc. can be exemplified. As to the substituted alkyl group, hydroxyalkyl group, halogenated alkyl group, cyanoalkyl group, etc. may be exemplified.
As to the amino acid in mercaptoacetylpolyamino acid, glycine, alanine, threonine, leucine, isoleucine, phenylalanine, valine, methionine, aspargic acid, glutamic acid, serine, tyrosine, asparagine, glutamine, etc. can be exemplified. These amino acids may be arranged repeatedly or at random, and among them, mercaptoacetylglycylglycylglycine may be used preferably.
As to embodiments of the bisphosphonic acid derivative represented by the formula (1), compounds represented by the following formulas (3) to (12) may be exemplified.
As to an example of introducing a functional group, accelerating urinary excretion, into bisphosphonic acid, there is a bio-adduct type compound being bonded bisphosphonic acid with the amino group in amino acid, and in the formula (1), when R is carboxyl group, the compound may be shown by the following formula (3):
HOOCxe2x80x94Yxe2x80x94Axe2x80x83xe2x80x83(3)
Specifically, in case of single lower molecular weight amino acid having carboxylic acid, it is preferably to bond bis-phosphonic acid thereto, for example, as shown in the formula (4), glycine adduct compound of N-(3,3-diphosphonopropionyl)glycine can be exemplified, wherein the glycine adduct compound has both carboxylic acid group and bisphosphonic acid group:
HOOCCH2NHCOCH2CH(PO3H2)2xe2x80x83xe2x80x83(4)
As to amino acids other than the glycine, there can be exemplified alanine, threonine, leucine, isoleucine, phenylalanine, valine, methionine, asparaginic acid, glutaminic acid, serine, tyrosine, asparagine, glutamine, etc. and these amino acids can be arranged repeatedly or at random.
The following formula (5) shows bisphosphonic acid derivative of a monomolecular structure type, which does not form polymer structure, wherein R in the above-mentioned formula (1) is the formula (2). There can be mentioned bisphosphonic acid derivative prepared by substituting an aromatic carboxylic acid or an aromatic aminocarboxylic acid with bisphosphonic acid, or by introducing bisphosphonic acid into the aromatic ring. 
For example, as shown in the following formula (6), 2-(2-iodobenzamido)-1,1-diphosphonoethane prepared by substituting the carboxylic acid in hippuric acid with bisphosphonic acid, which can be easily labeled with radioactive iodine and having excellent affinity to the bone and the property of efficient urinary excretion. 
Further, as shown in the following formula (7), 2-iodo-4-(4,4-diphosphonopropionamido)hippuric acid prepared by introducing bisphosphonic acid into the phenyl group and remaining the structure of glycine carboxylic acid in hippuric acid, can be easily labeled with radioactive iodine and has the property of being rapidly excreted into urine, thus, said compound is useful as a carrier or a precursor for agent for diagnosis or therapy of the bone disease. 
As shown in the following formulas (8) and (11), those bisphosphonic acid derivatives are functional group type derivatives prepared by introducing bisphosphonic acid into the metallic coordinating functional group which can form complex with a radioactive metal such as 99m-Technetium suitable for scintigraphy, or 186-Rhenium, 188-Rhenium effective as an in vivo a radiation source for bone disease therapy. As to the metallic coordinating functional group, the above-mentioned polyaminopolycarboxylic acid, mercaptoacetylpolyamino acid, etc. can be used. As to these examples, any compounds capable to form complex with a metal can be selected, such as diethylene-triaminepentaacetic acid (DTPA), ethylene cysteine dimer diethyl ester (ECD), 1,4,7,10-tetraazacyclododecane-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x2xe2x80x3-tetraacetic acid (DOTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-xcex1,xcex1xe2x80x2,xcex1xe2x80x3,xcex1xe2x80x2xe2x80x3-tetrakis(methylacetic acid) (DOTMA), 1,4,8,11-tetraazacyclododecane-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x2xe2x80x3-tetraacetic acid (TETA), mercaptoacetylglycylglycylglycine (MAG3). Among them, DTPA may be preferably used. Further, the bonding position of the metallic coordinating functional group with bisphosphonic acid may be any position and can be selected suitably.
Formula (8) shows a compound represented by formula (1) wherein R is a polyaminopolycarboxylic acid and said carboxyl group is substituted by R1 or R2. 
In formula (8), Y and A are defined previously in formula (1), R1 and R2 are each represents Yxe2x80x94A or Yxe2x80x94COOH, and when s=0, then R1 is Yxe2x80x94A; when s=1 and R1 is Yxe2x80x94A, then R2 is Yxe2x80x94COOH, when R1 is Yxe2x80x94COOH, then R2 is Yxe2x80x94A; when s=2 to 4 and R1 is Yxe2x80x94A, then R2 is Yxe2x80x94COOH; and when R1 is Yxe2x80x94COOH, then one of R2 is Yxe2x80x94A and another R2 is Yxe2x80x94COOH.
As to specific example of the bisphosphonic acid derivatives, wherein the carboxyl group of polyaminopolycarboxylic acid is substituted by bisphosphonic acid, 3,6-bis(carboxymethyl)-9-(((2,2-diphosphonoethyl)carbamoyl)methyl)-3,6,9-triazaundecanedicarboxylic acid is shown in formula (9), 
and 3,6-bis(carboxylmethyl)-6-(((2,2-diphosphonoethyl)carbamoyl)methyl)-3,6,9-triazaundecanedicarboxylic acid is shown in formula (10). 
Bisphosphonic acid derivative as shown in formula (11) is a compound wherein R in formula (1) is mercaptoacetylpolyamino acid. In formula (11), Y and A are each defined previously in formula (1), R3, R4, R5 and R6 are respectively Yxe2x80x94A or a hydrogen atom; and when R3 is Yxe2x80x94A, then R4, R5 and R6 are hydrogen atoms; when R4 is Yxe2x80x94A, then R3, R5 and R6 are hydrogen atoms; when R5 is Yxe2x80x94A, then R3, R4 and R6 are hydrogen atoms; and when R6 is Yxe2x80x94A, then R3, R4 and R5 are hydrogen atoms. 
As to preferable bisphosphonic acid derivative, N-mercaptoacetyl-2-[4-(4,4-diphosphonopropioneamide)butyl]glycylglycylglycine is exemplified as the formula (12). 
As to the radioactive nuclide to be used for radiolabeling the above-mentioned bisphosphonic acid derivatives or salts thereof, in accordance with applications, i.e., in vivo radioactive diagnostic imaging or in vivo radiotherapy, it is selected from the group consisting of 11-Carbon (11C), 15-Oxygen (15O ), 18-Fluorine (18F), 32-Phosphorus (32P), 52-Iron (52Fe), 59-Iron (59Fe), 62-Zinc (62Zn), 64-Copper (64Cu), 67-Copper (67Cu), 67-Gallium (67Ga), 81m-Krypton (81mKr), 81-Rubidium (8Rb), 87m-Strontium (87mSr), 89-Strontium (89Sr), 90-Yttrium (90Y), 99m-Technetium (99mTc), 111-Indium (111In), 115m-Indium (115mIn), 123-Iodine (123I), 125-Iodine (125I), 131-Iodine (131I), 133-Xenon (133Xe), 117m-Tin (117mSn), 153-Samarium (153Sm), 186-Rhenium (16Re), 188-Rhenium (188Re), 201-Thallium (202Tl), 212-Bismuth (212Bi), 213-Bismuth (213Bi) and 211-Astatine (211At). As to the nuclide for diagnostic imaging, 99m-Technetium, 111-Indium, 123-Iodine, etc. are preferably used, and as to the nuclide for radiotherapy, 117m-Tin, 153-Samarium, 186-Rhenium, 188-Rhenium, 125-Iodine, 131-Iodine, 211-Astatine, etc. are preferably used.
In the above-mentioned formula (1), the symbol Y is the bonding portion selected from any one of xe2x80x94(CH2)lxe2x80x94, xe2x80x94[(CH2)m(NHCO)r(CH2)n]qxe2x80x94, xe2x80x94[(CH2)m(CONH)r(CH2)n]qxe2x80x94, or xe2x80x94(CH2)oxe2x80x94Sxe2x80x94(CH2)pxe2x80x94, and k, l, m, n, o, p, q, r, are independently to each other, and are preferably selected from integers of k=0 or 1, l=0 to 6, m=0 to 6, n=1 to 6, o=0 to 6, p=0 to 6, q=1 to 6, r=1 to 6.
The salts of compounds of the present invention, are pharmaceutically acceptable salts of inorganic bases, for example salts of alkaline metal, such as lithium, sodium, potassium, etc.; salts of alkaline earth metal, such as calcium, magnesium, etc.; ammonium salt; salts of organic bases for example salts of methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, cyclohexylamine, ethanolamine, diethanolamine, morpholine, meglumine, etc; salts of basic amino acids for example salt of lysine, ornithine, arginine, etc. can be exemplified. Among them, sodium or potassium is used preferably, and particularly, a mixture of disodium salt with trisodium salt is preferable.
In the present invention, one embodiment of the bisphosphonic acid derivative labeled with radioactive nuclide is a radiolabeled compound which is prepared by labeling a compound represented by the formula (1) with radioactive nuclide, wherein R is a group labeled with radiohalogen or a radioactive transition metal; and A is a bisphosphonic acid of free form or salt thereof which does not participate in radiolabeling.
Japanese patent application Kohyo No. Hei 10-501218 discloses mono-, di- and polyphosphonate complexes labeled with 99m-Technetium, each of which has different composition in accordance with different preparation conditions such as heating in autoclave, heating by microwave, etc. This method is an attempt to improve the slow clearance of an radiotherapentic agent for bone disease due to the formation of polymer structure during the radiolabeling procedure. However, formation of radio metal complex of phosphonates having polymer structure is inevitable by such a method. In consideration of these circumustances, the present invention provides a bisphosphonic acid derivative labeled with a radioactive nuclide as a basic affinity material to the bone, and having the property of advantageously accumulating to the bone, by the formation of radiolabeled bisphosphonic acid derivative wherein the bisphosphonate part does not participate in the complex formation. Thus, one feature of the present invention is a radiohalogenated monomolecular bisphosphonic acid derivative of which bisphosphonate part remains the free form and retain the affinity to the bone like free bisphosphonate. Another feature is a radiolabeled monomolecular bisphosphonic acid derivative retaining the affinity to the bone, in which the bisphosphonate part does not participate in complex formation with a radioactive metal. This feature can be obtained when the complex forming ability of metal coordinating functional group of the bisphosphonic acid derivative is greater than that of bisphosphonate part. The difference of complex forming ability between the metal coordinating functional group and the bisphosphonate part can be proven by use of a related compound of the present invention. Thus, the fact that bisphosphonic acid does not participate in the complex formation can be proven by selecting conditions of labeling such as radioactive metal nuclides, concentrations, pH, reducing agents, etc. In the following Examples, co-existing labeling methods by use of DTPA or MAG3 with HMDP are mentioned. However, the all Examples are disclosing as examples only, and the present invention is not restricted only to the Examples.
By subjecting to labeling with a suitable radioactive nuclide, the compound of the present invention is useful as the active ingredient of a diagnostic agent for bone disease such as bone metastasis, osteoporosis, Pagetic disease, fracture, heterotropic ossification, osteolysis, etc., since the compound can be selectively incorporated into the bone system and can be rapidly excreted into urine. In case of applying a radiolabeled compound of the present invention for bone scintigraphy to find the diseased position of bone tumor, the compound is administered intravenously to mammals including human being, then the distribution of radioactivity in the whole body are determined by use of an instrument (e.g. gamma ray camera) commonly known in the diagnostic field.
A compound of the present invention can be applied for the purposes of therapy for bone pain palliation, chronic rheumatic arthritis and inflammatory osteonosis such as low back pain and the like, and also applied as carcinostatic agents for preventing bone metastasis of tumors and the like. Additionally, a radiolabeled bisphosphonic acid derivative of the present invention can be used for diagnostic purposes of evaluating pharmacological effects such as selection of drugs and judgement of effects of drugs, etc.
As to the administration forms of drugs, bisphosphonic acid derivative of the present invention is provided as in the form of an aqueous solution or lyophilized preparation thereof, and can be provided as a kit form for labeling the compound with a radioactive nuclide by supplying the aqueous solution or lyophilized preparation comprising reducing agents, stabilizing agents and the like. The kit form for labeling the compound with a radioactive nuclide comprising a bisphosphonic acid derivative of the present invention is preferably supplied as in the form of a lyophilized preparation. In case of using, the lyophilized preparation is dissolved in a suitable diluent and labeled with a radioactive nuclide, then administered. The aqueous solution containing the above-mentioned bisphosphonic acid derivative can be administered after formulating by conventional methods used in pharamceutical practice or by labeling with a radioactive transition metal in the presence of a non-metallic reducing agent according to the present invention.
In case of radiohalogenation of the above-mentioned bisphosphonic acid derivative, a precursor which is previously substituted with a halogen or a metalloalkyl group can be used. As to the halogen, fluorine, bromine, iodine, etc. can be used, and as to the metalloalkyl group, trialkyl tin and the like represented by the formula Sn(R3) can be exemplified, and as to the alkyl group, such as methyl group, ethyl group, propyl group, butyl group can be used. Preferably, trimethyl tin or tributyl tin may be used.
In conducting the radiohalogenation using the precursor being previously substitued a bisphosphonic acid derivative with a halogen or metalloalkyl group, the kit preparation for radiolabeling as in the form of lyophilized or solution comprising the above-mentioned precursor can be used. The radiohalogenation of the precursor may be conducted by methods known in the art, such as substitution reaction or exchange reaction. Conventionally used additives such as oxidizing agents, stabilizing agents, buffering agents, vehicles, etc. may be added to the above-mentioned kit preparation for radiolabeling. For example, if necessary, chroramine T, hydrogen peroxide and the like can be added as the oxidizing agents in conducting the labeling reaction. This labeling reaction may be conducted by a known method, and temperature, concentration, pH and other conditions are not specifically restricted.
In conducting labeling with a radioactive transition metal, reducing agents to be used for chemical reduction of peracid such as pertechnetate (Tc-99m) and the like, generally metals such as tin, zinc, iron, etc. or metal compounds such as chromium chloride, chromium acetate, etc. or combinations of tin chloride, tin fluoride, etc. with organic acid or inorganic acid may be used. Further, it is not limited to metal compounds, thus, non-metallic reducing agents, such as sodium diphenylphosphinobenzene-3-sulfonate, formamidinesulfonic acid or glucoheptanoic acid and the like can be used. Dithionic acid, sodium hydrogensulfite can also be used. Additionally, by use of a compound, for example, organic acids such as gluconic acid, ascorbic acid, citric acid or the like, carbohydrate such as mannose, which forms relatively unstable complex, a compound of the present invention can be labeled with radioactive transition metal through ligand exchange reaction. In this case, the reaction conditions such as temperature, concentration, pH and others are not specifically restricted, and the reaction can be conducted at an ambient temperature or under heating, and the reducing agent may be used suitably depend on the reaction conditions.
Further, a pharmaceutical preparation of the present invention may comprise physiologically acceptable buffering agents (e.g., physiological saline, a pH controlling agents, such as acetic acid, phosphoric acid, carbonic acid, tris(hydroxymethyl)aminomethane, and the like) and other physiologically acceptable additives (e.g., stabilizing agents such as ascorbic acid, paraben, dissolving agents, vehicles such as D-mannitol and the like).
A compound of the present invention can be used similarly to conventional diganostic agents or therapeutic agents, for example, a liquid preparation is administered by injection to mammals including human-being. Administrative dosage of the compound is substantially similar to that of conventional diagnostic or therapeutic agents, the diagnostic agent is administered in a range of about 3 to 25 MBq/kg, preferably 6 to 12 MBq/kg, and the therapeutic agent is administered depending on kind of radioactive nuclide. The administrative dosage may be adjusted suitably depending on kind of the compounds, kind of the radioactive nuclides, age of the patient, body wight of the paitent, symptoms, method of administration, combined use with other drugs, and other factors.